39 lines
917 B
Python
39 lines
917 B
Python
from migen.fhdl.structure import *
|
|
|
|
(SP_WITHDRAW, SP_CE) = range(2)
|
|
|
|
class RoundRobin:
|
|
def __init__(self, n, switch_policy=SP_WITHDRAW):
|
|
self.n = n
|
|
self.request = Signal(self.n)
|
|
self.grant = Signal(max=self.n)
|
|
self.switch_policy = switch_policy
|
|
if self.switch_policy == SP_CE:
|
|
self.ce = Signal()
|
|
|
|
def get_fragment(self):
|
|
if self.n > 1:
|
|
cases = {}
|
|
for i in range(self.n):
|
|
switch = []
|
|
for j in reversed(range(i+1,i+self.n)):
|
|
t = j % self.n
|
|
switch = [
|
|
If(self.request[t],
|
|
self.grant.eq(t)
|
|
).Else(
|
|
*switch
|
|
)
|
|
]
|
|
if self.switch_policy == SP_WITHDRAW:
|
|
case = [If(~self.request[i], *switch)]
|
|
else:
|
|
case = switch
|
|
cases[i] = case
|
|
statement = Case(self.grant, cases)
|
|
if self.switch_policy == SP_CE:
|
|
statement = If(self.ce, statement)
|
|
return Fragment(sync=[statement])
|
|
else:
|
|
return Fragment([self.grant.eq(0)])
|